Reporting of Multiple IF/RAT Layer Restrictions

ABSTRACT

In one aspect, the invention provides a multi-modal user equipment (UE) configuration method. In some embodiments, the method includes: configuring the UE so that it supports a plurality of radio access technologies (RATs), wherein each of the plurality of RATs is associated with a predetermined maximum number of layers that the UE may be instructed by a network node to monitor simultaneously; configuring the UE so that it is operable to transmit to the network node RAT capability information identifying the plurality of RATs supported by the UE; and configuring the UE to monitor simultaneously not more than X layers associated with one of the plurality of RATs, wherein X is less than the predetermined maximum number of layers associated with the RAT.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 12/507,376,filed on Jul. 22, 2009, which i) claims the benefit of provisionalpatent application No. 61/088,483, filed on Aug. 13, 2008 and ii) is acontinuation of international patent application no. PCT/SE2009/050011,filed on Jan. 12, 2009. The above-identified applications areincorporated by reference herein.

TECHNICAL FIELD

The present invention relates to mobile communications in environmentshaving multiple radio access technologies, each with one or more layersavailable for mobility of user equipments (UEs).

BACKGROUND

Evolving radio communications technologies create mobile communicationsenvironments having variable sets of radio access technologies (RATs).For example, in a given geographical area, the following RATs may beavailable: Wideband Code Division Multiple Access (WCDMA), UniversalTerrestrial Radio Access Network (UTRAN) and Evolved UTRAN (E-UTRAN). Inanother geographical area, a different set of RATs may be available; forexample, only Global System for Mobile communications (GSM) may beavailable. A mobile terminal user would want a mobile terminal capableof operating in both areas. Thus, mobile terminal manufacturers offermobile terminals (a.k.a., user equipments (UEs)) capable of operatingwith multiple RATs (i.e., multi-mode UEs).

Users also desire seamless UE mobility within and between geographicareas. Thus, manufacturers of UEs face the further demand for multi-modeUEs with a high degree of RAT interoperability to support transparentmobility. For example, given the mobile communications environmentdiscussed in the preceding paragraph, a user may wish to initiate a callin the geographic area covered by GSM and have full call continuity asthe UE travels from that area to the area covered by E-UTRAN. Thus, theUE must be capable of monitoring channels in both RATs while a call isin progress.

Fortunately, E-UTRAN, often referred to as Long Term Evolution (LTE),provides for such multi-RAT connected mode mobility. However, LTEimposes a burden on UEs to monitor up to three layers (i.e., non-servingfrequency carriers), as instructed by the network, for each RATsupported, regardless of the number of RATs that are supported by theUE. On each layer the UE is required to monitor multiple cells e.g.between 4-6 cells per layers depending upon the type of RAT. Thus, LTErequires a multi-mode UE capable of operating with, for example, fourRATs (e.g. multi-mode UE supporting LTE FDD, LTE TDD, UTRAN FDD andUTRAN TDD), to monitor up to twelve layers in parallel in a mobilecommunications environment having those four RATs. Assuming 5 cells tobe monitored per layers, such a UE will have to monitor in total 60cells in parallel (i.e., using the same gap pattern.) Parallelmonitoring implies that UE monitors all the requested layers during asingle periodic gap. In LTE, gap patterns with two different periodicityare define: 6 ms gap occurring every 40 or 6 ms gap occurring every 80ms. Only one of them can be activated at a time. The LIE layermonitoring requirements means that a UE manufacturer must weighconsiderable cost/benefit tradeoffs for each additional RAT supported bythe UE as each additional supported RAT means that additional memory,radio, and computational resources are required to accommodate theincreased layer monitoring requirements. Thus, it is desirable for theUE to have some control over layer monitoring requirements imposed bythe network.

SUMMARY

In one aspect, the present invention provides a method performed by abase station. In some embodiments, the method includes the followingsteps: (1) receiving capability information from a UE, where thecapability information includes RAT capability information identifying aset of RATs supported by the UE, where each RAT is associated with apredetermined maximum number of layers that the UE may be instructed tomonitor simultaneously, were the predetermined maximum number of layersis a standardized value; (2) for at least one of the RATs in the set ofRATs supported by the UE, determining a number of layers of the RAT toinstruct the UE to monitor, where the determined number of layers isless than the predetermined maximum number of layers associated with theRAT; and (3) transmitting to the UE RAT layer monitoring information,wherein the RAT layer monitoring information indicates the determinednumber of layers that the UE should monitor on the RAT. In someembodiments, the determination of the number of layers of the RAT toinstruct the UE to monitor is based on, at least in part, at least someof the received capability information.

In some embodiments, the method further includes a step of storingconfiguration information that, for each of sets of RATs, associates anumber with at least one RAT included in the set, where the numberrepresents a number of layers associated with the RAT. The determiningstep further includes accessing the configuration information and usingthe configuration information to determine the number of layersassociated with the RAT to instruct the UE to monitor.

In some embodiments, the step of using the configuration informationincludes finding the set of RATs included in the configurationinformation that matches the RATs identified by the RAT capabilityinformation.

In some embodiments, the capability information further comprises RATlayer capability information indicating that the UE is configured tomonitor less than the predetermined maximum number of layers associatedwith at least one of the RATs included in the set of RATs. In theseembodiments, the RAT layer capability information may comprise: (1) foreach RAT included in the set of RATs, a number associated with the RAT,the number representing a maximum layer monitoring capability; (2) forat least one of the RATs included in the set of RATs, a numberassociated with the RAT, the number representing a maximum layermonitoring capability and the number being less than the predeterminedmaximum number associated with the RAT; or (3) for each RAT included inthe set of RATs, a single bit, wherein the value of the bit identifieswhether or not the UE is configured to monitor the predetermined maximumnumber of layers associated with the RAT.

In another aspect, the invention provides an improved base station. Insome embodiments, the improved base station includes: (1) a receiveroperable to receive capability information transmitted from a UE, wherethe capability information includes RAT capability informationidentifying a set of RATs supported by the UE, where each RAT includedin the set is associated with a predetermined maximum number of layersthat the UE may be instructed to monitor; (2) a RAT layer determiningmodule configured to determine the number of layers of a RAT to instructthe UE to monitor, where the determined number of layers may be (a)equal to the predetermined maximum number of layers associated with theRAT or (b) less than the predetermined maximum number of layersassociated with the RAT, and the RAT layer determining module isconfigured to make the determination based, at least in part, on atleast some of the received capability information; (3) a transmitteroperable to transmit to the UE RAT layer monitoring information, wherethe RAT layer monitoring information indicates the number of layers ofthe RAT that the UE should monitor.

In some embodiments, the base station further includes a data storagedevice for storing configuration information that, for each of sets ofRATs, associates a number with at least one RAT included in the set,where the number represents a number of layers associated with the RATand the RAT layer determining module may be configured to determine thenumber of layers by accessing the configuration information and usingthe configuration information to determine the number of layersassociated with the RAT to instruct the UE to monitor.

In some embodiments, the RAT layer determining module is configured touse the configuration information by finding the set of RATs included inthe configuration information that matches the RATs identified by theRAT capability information.

In another aspect, the invention provides a method performed by a UE forinforming a network node of the UE's RAT capabilities. In someembodiments, the method includes the steps of: (1) determining whethercapability information should be sent to the network node and (2)transmitting capability information to the network node in response todetermining that the capability information should be sent to thenetwork node, were the transmitted capability information includes: (a)RAT capability information identifying RATs supported by the UE (each ofthe RATs being associated with a predetermined maximum number of layersthat the UE may be instructed by the network node to monitor) and (b)RAT layer capability information indicating that the UE is configured tomonitor less than the predetermined maximum number of layers associatedwith at least one of the RATs.

In some embodiments the method further includes: receiving from thenetwork node RAT layer monitoring information, where the RAT layermonitoring information includes information indicating the number oflayers that the UE should monitor on a specified RAT, and, in responseto receiving the RAT layer monitoring information, monitoring not morethan the number of layers on the specified RAT, wherein the number oflayers is less than the predetermined maximum number of layersassociated with the RAT.

In some embodiments, the step of monitoring the layers on the specifiedRAT comprises identifying new cells belonging to the layers. In someembodiments, the step of monitoring the layers on the specified RATfurther comprises: performing one or more downlink measurements on theidentified new cells; and/or evaluating one or more events associatedwith one or more of the identified new cells.

In another aspect, the invention provides an improved UE. In someembodiments, the improved UE includes: (1) a receiver operable toreceive information transmitted from a network node; (2) a capabilityinformation module configured to create a message comprising capabilityinformation, the capability information comprising (a) radio accesstechnology (RAT) capability information identifying a plurality of RATssupported by the UE, wherein each of the plurality of RATs is associatedwith a predetermined maximum number of layers that the UE may beinstructed by the network node to monitor and (b) RAT layer capabilityinformation indicating that the UE is configured to monitor less thanthe predetermined maximum number of layers associated with at least oneof the plurality of RATs; (3) and a transmitter operable to transmit themessage to the network node.

In another aspect, the invention provides a multi-modal UE configurationmethod. In some embodiments, the method includes the following steps:(1) configuring the UE so that it supports a plurality of radio accesstechnologies (RATs), wherein each of the plurality of RATs is associatedwith a predetermined maximum number of layers that the UE may beinstructed by a network node to monitor simultaneously; (2) configuringthe UE so that it is operable to transmit to the network node capabilityinformation, the capability information comprising RAT capabilityinformation identifying the plurality of RATs supported by the UE; and(3) configuring the UE to monitor simultaneously not more than X layersassociated with one of the plurality of RATs, wherein X is less than thepredetermined maximum number of layers associated with the RAT. In someembodiments, the UE is configured to monitor layers associated with aRAT by identifying new cells belonging to the layers and performing oneor more downlink measurements on the identified new cells and/orevaluating one or more events associated with one or more of theidentified new cells.

The above and other aspects and embodiments are described below withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and form partof the specification, illustrate various embodiments of the presentinvention and, together with the description, further serve to explainthe principles of the invention and to enable a person skilled in thepertinent art to make and use the invention. In the drawings, likereference numbers indicate identical or functionally similar elements.

FIG. 1 illustrates a mobile radio communications system.

FIG. 2 illustrates a UE and a base station communicating information andinstructions in accordance with an embodiment of the invention.

FIGS. 3A-3E illustrate capability message formats according to variousembodiments of the invention.

FIG. 4 illustrates a method which may be implemented at base station, orother node, in accordance with an embodiment of the invention.

FIG. 5 illustrates a method which may be implemented at a base stationor other node in accordance with an embodiment of the invention.

FIG. 6 illustrates a method which may be implemented by a UE inaccordance with an embodiment of the present invention.

FIG. 7 illustrates a method of manufacturing a UE in accordance with anembodiment of the present invention.

FIG. 8 illustrates a base station in accordance with an embodiment ofthe present invention.

FIG. 9 illustrates a UE in accordance with an aspect of the presentinvention.

DETAILED DESCRIPTION

As illustrated in FIG. 1, an exemplary mobile radio communicationssystem 100 includes multiple radio base stations such as eNode B 104,Node B 106, eNode B 108, and Base Transceiver Station (BTS) 110. Theradio base stations may each support one or more cells in RATs such as:

-   -   E-UTRA Frequency Division Duplexing (FDD),    -   E-UTRA Time Division Duplexing (TDD),    -   UTRA FDD,    -   UTRA TDD,    -   CDMA2000 High Rate Packet Data (HRPD),    -   CDMA2000 1x Radio Transmission Technology (RTT), and    -   GSM.        System 100 may also include multiple mobile terminals, such as        User Equipment (UE) 102.

UE 102 is capable of mobility between the cells of mobile radiocommunications system 100. Generally, UE mobility refers to both idlemode mobility (UE cell reselection) and connected mode mobility(involving handover of calls in progress). Cell reselection is generallya UE autonomous function not requiring the intervention of the servingcell, although some UE behavior may be controlled by broadcast systemparameters and performance specifications. Connected mode mobility, onthe other hand, is fully controlled by the network through explicit UEspecific commands and by performance specifications.

Mobility decisions are based on downlink measurements. Downlinkmeasurements include intra-frequency, inter-frequency (IF), andinter-RAT (IRAT) measurements. These measurements may includeidentifying new or unknown cells, measuring signal strength ofidentified cells, measuring signal quality of identified cells, etc.Using one or more measurements, the UE may report the measurementsand/or one or more events, such as the signal strength of the strongesttarget cell on carrier frequency (layer) rising above a threshold. Thenetwork uses the reported measurement results and/or event to takemobility actions (e.g. sending a handover command to the UE). In LTE,the UE performs connected mode inter-frequency and IRAT measurements inperiodic gaps which occur during time slots having no downlinktransmissions. These time slots exist for the purpose of enabling the UEto measure on inter-frequency cells or on other RATs. A single gappattern may be shared for all measurements on different inter-frequencyand RAT layers.

As discussed in the background section above, a prior art UE may berequired to perform and report measurements of cells distributed over alarge number of layers to support various intra-frequency,inter-frequency, and IRAT mobility scenarios.

In LTE, downlink quality measurements specified for mobilitydeterminations include reference symbol received power (RSRP) andreference symbol received quality (RSRQ). These measurements areperformed by the UE on a cell level basis on reference symbols.

In UTRAN FDD (WCDMA), downlink quality measurements for mobility reasonsinclude common pilot channel (CPICH) RSCP, CPICH Ec/No, and UTRA carrierRSSI [1]. The first two of the above measurements are performed by theUE on cell level basis. UTRA carrier RSSI is measured over the entirefrequency carrier. In cdma2000 1x RTT and HRPD systems, cdma2000 PilotStrength and HRPD Pilot Strength respectively are measured and used formobility determinations. In GSM, GSM carrier RSSI is used for all typesof mobility decisions.

In the RATs described above, one frequency carrier is provided to eachcell, with GSM as an exception. In GSM, a frequency band is subdividedinto frequency carriers and each cell provided with a subset of thetotal number of frequency carriers available.

In order to guarantee good mobility performance, the E-UTRANspecification provides for minimum UE requirements for measurementperformance and reporting of downlink measurements. One active(connected) mode requirement is identification delay of unknown cellsfor the given received level of the corresponding synchronization andreference signals. This is the time required to search an unknown celland to decode its physical layer identity. Once the cell is identified,the UE continues measuring and evaluating it. Another active moderequirement is the minimum number of identified cells for which UE issupposed to report the CPICH measurements. Other requirements includeabsolute and relative accuracies and the measurement period over whichthe specified measurement accuracies of the reported cells arefulfilled. Monitoring of a layer is a general term referring to cellidentification and/or measurement process. Thus, in some embodiments,monitoring a layer means that the UE identifies cells belonging to thelayer and then performs one or more downlink measurements on theidentified new cells and/or evaluates one or more events associated withone or more of the identified new cells.

Minimum layer monitoring requirements are specified separately forE-UTRA intra-frequency TDD/FDD, E-UTRA inter-frequency FDD/TDD, and IRAT(including UTRA FDD/TDD, GSM, HRPD and cdma2000 1x RTT). In particular,UEs are required to measure a number of carrier frequencies per RAT.Furthermore, a UE should be able to measure a certain number of cellsper carrier frequency per RAT. For example, let M be the number of RATssupported by the UE, K be the required number of cells per carrierfrequency per RAT that UE should be able to measure, and N be therequired carrier frequencies per RAT to be supported by the UE. In thisscenario, the network can theoretically instruct the UE tosimultaneously measure M×K×N cells in total.

For simplicity and consistency, this disclosure refers to a carrierfrequency as a layer. LTE requirements for layer monitoring per RAT mayinclude:

-   -   3 E-UTRA FDD layers (for IF measurements),    -   3 E-UTRA TDD layers (for IF measurements),    -   3 UTRA FDD layers (for RAT measurements),    -   3 UTRA TDD layers (for RAT measurements),    -   3 HRPD carriers,    -   3 cdma2000 1x carriers, and    -   1 GSM layer (corresponding to 32 GSM carriers).

As can be seen, a UE capable of supporting all or even a larger numberof RATs would be required to perform a large number of parallelmeasurements. In the worst case, the total number of layers, includingone GSM layer, is nineteen, an exorbitant number.

Because all combinations of E-UTRA inter-frequency and RATs are unlikelyto be deployed in one geographic area by a single operator, a UE islikely to be requested to monitor only a subset of IF/RAT layers at atime. Similarly, many UEs will be capable of supporting combinations oflayers corresponding to typical scenarios. Exemplary deploymentscenarios are listed in table 1.

TABLE 1 Sce- IF/RAT nario layers to be No. IFs and RATs monitored 1E-UTRAN FDD IF, UTRAN FDD and GSM 7 2 E-UTRAN TDD IF, UTRAN TDD and GSM7 3 E-UTRAN FDD IF, HRPD and cdma2000 1x RTT 9 4 E-UTRAN TDD IF, HRPDand cdma2000 1x RTT 9 5 E-UTRAN FDD IF, E-UTRAN TDD, UTRAN 10 FDD andGSM 6 E-UTRAN FDD IF, E-UTRAN TDD, UTRAN 10 TDD and GSM 7 E-UTRAN FDDIF, E-UTRAN TDD, UTRAN 13 TDD, UTRAN FDD and GSM 8 E-UTRAN TDD IF,E-UTRAN FDD IF, 12 HRPD and cdma2000 1x RTT

It may be observed from the above listed scenarios in Table 1 that, inmany cases, a UE will not be required to simultaneously monitor morethan ten layers. However, in some scenarios, such as scenarios 7 and 8,the UE will be required to monitor more than ten layers.

Because the number of RATs supported by a UE is a UE capability, therewill be UEs in the market with differing RAT capabilities. UEmanufacturers will build UEs according to typical deployment scenariosand market needs. Nevertheless, UE manufacturers should not bediscouraged from manufacturing UEs capable of supporting more RATsbecause the UE would require greater radio, storage, and processingresources to monitor and report on the greater number of layers; rather,the UE should be allowed some control of the numbers of layers to bemonitored, thus reducing UE complexity and cost. Such control wouldprovide relaxation regarding maximum numbers of layer monitoring per RATand should be acceptable for the network as not all combinations of IFsand RATs will be used in one location. Also, not all measurements aretypically needed at a single time as this could require the UE to spendtime performing measurements practically indefinitely.

The UE may not need relaxation in all situations. For example, scenarios1-5 in Table 1 show that the UE should be able to handle at least tendifferent layers on various RATs (including one GSM layer). Ten layers(or another suitable threshold) may be a manageable number of layers tomonitor for some UE architectures. Thus, a multi-RAT UE that wouldotherwise be required to support more than ten layers should be allowedto implement a lower number of layers than the standardized values. Inthis case, the network should be informed about the reduction to beapplied. The network must have information regarding UE mobilitymeasurement capabilities in to order be able to instruct the UE tomeasure cells and layers for which the UE has capability and capacity.

Therefore, various embodiments of the present invention provide forvarious means of reporting by a UE 102 and instructing a UE 102 as tolayer monitoring requirements. In accordance with embodiments of theinvention, UE 102 transmits capability information 202 to eNode B 104illustrated in FIG. 2. eNode B 104 determines layer monitoringrequirements and transmits layer monitoring instructions 204.

In an exemplary embodiment of the present invention as illustrated inFIG. 3A, capability information 202 consists of a list of supported RATs301. According to this embodiment, the list of supported RATs 301 maycorrespond to a predefined scenario for relaxation of layer monitoringrequirements as illustrated in Table 2. In one aspect of thisembodiment, bits in an ordered bit-map could represent UE support (orlack of support) for a given RAT. In accordance with this aspect of theembodiment, the UE transmit to a base station information correspondingto one of the predefined scenarios. According to the example illustratedin FIG. 3A, capability information 202 indicates that the UE 102supports a scenario having all seven IF/RATs indicated in the LTEmobility specification. Such a multi-RAT UE may implement a layerrelaxation as indicated, for example, in scenario 9 in Table 2 below.

TABLE 2 Frequency Layers per RAT Predefined E-UTRA E-UTRA UTRA UTRAcdma2000 Maximum Scenario No FDD IF TDD IF FDD TDD GSM HRPD 1x RTTlayers Comments 1 3 — 3 — 1 — — 7 No relaxation 2 — 3 — 3 1 — — 7 Norelaxation 3 3 — — — — 3 3 9 No relaxation 4 — 3 — — — 3 3 9 Norelaxation 5 3 3 3 — 1 — — 10 No relaxation 6 3 3 — 3 1 — — 10 Norelaxation 7 3 2 2 2 1 — — 10 Relaxation up to 3 layers as compared to 7in table 1 8 3 3 — — — 2 2 10 Relaxation up to 2 layers as compared to 8in table 1 9 2 2 2 2 1 2 2 13 Relaxation up to 6 layers assuming allIF/RAT

One advantage of having predefined sets of layer monitoring maximums perRAT is that the UE can inform the network of its capabilities byreferring to the scenario(s) it is capable of handling. Note thatscenarios 1-6 in Table 2 correspond to scenarios 1-6 in Table 1.Scenarios 7 and 8, however, provide for a relaxation of the UEcapability as compared to scenarios 7 and 8 in Table 1. Scenario 9represents the case where all RAT layers are to be supported, albeitwith reduced numbers of layers monitored per RAT relative to LTEstandardized numbers.

In another embodiment illustrated in FIG. 3B, capability infoiination202 consists of a list of RATs 302 supported by the UE 102 and acorresponding list of numbers of layers 303. In this embodiment, UE 102reports how many layers it supports per RAT. In one aspect of thisembodiment, capability information 202 may consist only of an orderedlist of numbers of layers 303, where a position in the list correspondsto a RAT.

In some embodiments, if the total standard number of layers to bemonitored for the RATs supported by UE 102 as specified in a standardwould exceed a threshold T (e.g., 10 layers), then UE 102 may implementS-D layers per RAT, provided that S-D is not lower than threshold T,where S is the number of layers per RAT corresponding to a fullcapability as defined in, for example, an LIE specification and D is apredefined number (e.g., 1). In this embodiment, the chosen RAT(s) towhich reduction is applied is UE implementation dependent since there isno pre-defined value. Thus, UE 102 reports the number of layers itsupports for each RAT it supports. For the example illustrated in FIG.3B, UE capability information 202 indicates that UE 102 will supportmonitoring of 3 E-UTRA FDD layers, 2 E-UTRA TDD layers, 2 UTRA FDDlayers, 2 UTRA TDD layers, and 1 GSM layer.

In another embodiment, as illustrated in FIG. 3C, capability information202 consists of a list of supported RATs 304 and corresponding layercapability information 305. In this embodiment, UE 102 explicitlyreports its layer capability fora RAT only if the number of supportedlayers for the RAT is less than that corresponding to the standardizednumber (i.e., the requirement specified in a standard such as, forexample, 3GPP TS 36.133, “Evolved Universal Terrestrial Radio Acess(EUTRA); Requirements for support of radio resource management”). Thus,if for a particular RAT UE 102 does not explicitly report its layercapability for the RAT, this implies that UE 102 is fully capable ofsupporting the standardized number of layers for the RAT. For theexample illustrated in FIG. 3C, capability information 202 indicatesthat UE 102 will support monitoring of 2 E-UTRA TDD layers, 2 UTRA FDDlayers, 2 UTRA TDD layers, and 1 GSM layer. Additionally, the capabilityinformation indicates that UE 102 is capable of supporting E-UTRA FDDand will support monitoring of the standard specified number of layersin this IF/RAT.

In another embodiment, as illustrated in FIG. 3D, capability information202 consists of a list of RATs 306 and corresponding layer capabilityinformation 307. In this embodiment, UE 102 reports whether it supportsfull layer monitoring capability per RAT or not (i.e., 1 bit ofinformation per inter-frequency or RAT scenario). In this embodiment,the network can specify a certain minimum number of layers for each RAT.Thus, a UE not supporting full capability would imply the minimum value.In the example illustrated in FIG. 3D, capability information 202indicates that UE 102 will support monitoring of E-UTRA FDD, E-UTRA TDD,UTRA FDD, UTRA TDD, and GSM layer. The capability information alsoindicates that UE 102 will support monitoring of the standard number oflayers for E-UTRA FDD and GSM and will only support monitoring a reducednumber of layers for E-UTRA TDD, UTRA FDD, and UTRA TDD. For these RATs,the number of layers UE 102 may be instructed to monitor is reduced by apredetermined amount (e.g., 1) from the standardized number.

In another embodiment, as illustrated in FIG. 3E, capability information202 consists of list 308 and indicator bit 309. List 308 indicates whichRATs are supported by UE 102 and indicator bit 309 indicates whether UE102 supports a reduced number of layers for monitoring of one or more ofthe listed RATs. In this embodiment, the network can specify a certainminimum number of layers for each RAT. Thus, a UE not supporting fullcapability would imply the minimum value. That is, if bit 309 is set tozero (0), this would indicate that the UE is not capable of monitoringthe standard number of layers and the network will assume that the UEcan only handle the minimum number of layers for each RAT.

In the embodiments illustrated in FIGS. 3A-3E, the UE capability withrespect to the GSM RAT may be assumed to be one layer, corresponding to32 GSM carriers, without this being explicitly reported by UE 102.

Referring now to FIG. 4, FIG. 4 is a flow chart illustrating a process400, according to an embodiment of the invention, that is performed by abase station (e.g., base station 110, 104, 108) or other node. Process400 may begin in step 402, where the base station receives RATcapability information 202 from the UE 102 (e.g., base station receiveson of the messages 301, 302, 304, 306 or 308). In step 404, the basestation uses the received capability information to determine the numberof layers L associated with a RAT to instruct UE 102 to monitor. L maybe less than a standard set maximum number of layers S associated withthe RAT. In step 406, the base station transmits layer monitoringinstructions to UE 102, instructing UE 102 to monitor L of the RATlayers. Preferably, step 404 is performed for each RAT that the UEsupports as indicated in the RAT capability information.

Referring now to FIG. 5, FIG. 5 is a flow chart illustrating a process500, according to some embodiments, for performing step 404 (that is,for determining the number of layers L of a RAT to instruct the UE tomonitor). Process 500 may begin in step 502, where the base stationstores configuration information that defines a set of RAT scenarios(see e.g., the scenario table shown in Table 2). That is, the basestation stores configuration information that, for each of a pluralityof sets of RATs (i.e., plurality of RAT scenarios), associates a numberwith at least one RAT included in the set of RATs, wherein the numberrepresents a number of layers associated with the RAT. For example, foreach RAT scenario defined by the configuration information, theconfiguration information includes, for each RAT in the scenario,information identifying the number of layers L of the RAT that the basestation should instruct the UE to monitor.

In step 504, the base station obtains the UE's capability information301, which capability information 301 identifies a RAT scenario (i.e.,the set of RATs supported by the UE).

In step 506, the base station access the configuration information todetermine the RAT scenario included in the set of RAT scenarios thatmatches the RAT scenario reported by the UE. That is, the base stationfinds the set of RATs included in the configuration information thatmatches the set of RATs identified by the RAT capability informationreceived in step 504.

In step 508, the base station determines, for each RAT identified bycapability information 301, the number of layers L associated with theRAT in the scenario determined in step 506. This number of layers Lrepresents the number of layers of the RAT that the base station willinstruct the UE to monitor.

In other embodiments, the step of determining the number of layers L ofa RAT to instruct the UE to monitor is performed without using ascenario table. For example, as discussed above with reference to FIGS.3B-E, the UE may transmit capability information to abuse station thatexplicitly or implicitly identifies the UE layer monitoring capabilityfor each RAT supported by the UE. Thus, the determination as to thenumber of layers L of a RAT to instruct the UE to monitor is based on,at least in part, the capability information the UE transmits to thebase station.

Referring now to FIG. 6, FIG. 6 is a flow chart illustrating a process600, according to some embodiments, that may be performed by UE 102.Process 600 may begin in step 602, where UE 102 receives informationfrom one or more network nodes (e.g., a base station shown in FIG. 1).In step 604, UE 102 determines whether UE 102 should transmit capabilityinformation to the network node.

In step 606, UE 102, in response to determining that UE 102 shouldtransmit capability information to the network node, transmit thecapability information to the network node. As discussed above withreference to FIGS. 3B-3E, the capability information may include RATcapability information identifying a set of RATs supported by the UEtogether with RAT layer capability information indicating that the UE isconfigured to monitor less than a predetermined maximum number of layersassociated with at least one of the RATs in included in the set. Forexample, as shown in FIG. 3B, the RAT layer capability information mayinclude, for each RAT included in the set of RATs, a number associatedwith the RAT, where the number represent the maximum number of layers ofthe RAT the UE should be instructed to monitor. And, as shown in FIG.3D, the RAT layer capability information may include, for each RATincluded in the set of RATs, a one-bit value, where the value of the onebit identifies whether the UE is capable of monitoring a predeterminedmaximum number of layers associated with the RAT that is defined in astandard.

In step 608, UE 102 receives from the network node RAT layer monitoringinformation, wherein the RAT layer monitoring information comprisesinformation indicating the number of layers associated with a RAT thatthe UE should monitor. In step 610, in response to receiving the RATlayer monitoring information, UE 102 monitors not more than X layersassociated with the RAT, wherein X is less than the predeterminedmaximum number of layers associated with the RAT.

Referring now to FIG. 7, FIG. 7 is a flow chart illustrating a process700, according to some embodiments, for making a UE 102. Process 700 maybegin in step 702, where UE 102 is configured to support multiple RATs.In step 704, UE 102 is configured to transmit RAT layer monitoringcapability information 202 to a network node. For example, the UE 102may be configured to transmit the capability information described abovewith reference to FIGS. 3B-3E. In step 706, UE 102 is configured tomonitor fewer layers in a given RAT than a predetermined maximum numberof layers in the RAT that is defined in a standard.

Referring now to FIG. 8, FIG. 8 is a functional block diagram of basestation 106 according to some embodiments of the invention. As shown,base station 106 may comprise a data processing system 802 (e.g., one ormore microprocessors), a data storage system 806 (e.g., one or morenon-volatile storage devices) and computer software 808 stored on thestorage system 806. Configuration parameters 810 (e.g., the abovescenario table) may also be stored in storage system 806. Base station106 also includes transmit/receive (Tx/Rx) circuitry 804 fortransmitting data to and receiving data from UE 102 and transmit/receive(Tx/Rx) circuitry 805 for transmitting data to and receiving data from,for example, a core network node 888. Software 808 is configured suchthat when processor 802 executes software 808, base station 106 performssteps described above (e.g., steps described above with reference to theflow charts shown in FIGS. 4 and 5). For example, software 808 mayinclude: (1) computer instructions (e.g., a RAT layer determiningmodule) for determining the number of layers associated with a RAT toinstruct a UE to monitor, wherein the determined number of layers may be(a) equal to a predetermined maximum number of layers associated withthe RAT or (b) less than said predetermined maximum number of layersassociated with the RAT. The RAT layer determining module may beconfigured to make the determination based, at least in part, oncapability information received from the UE.

Referring now to FIG. 8, FIG. 8 is a functional block diagram of basestation 106 according to some embodiments of the invention. As shown,base station 106 may comprise a data processing system 802 (e.g., one ormore microprocessors), a data storage system 806 (e.g., one or morenon-volatile storage devices) and computer software 808 stored on thestorage system 806. Configuration parameters 810 (e.g., the abovescenario table) may also be stored in storage system 806. Base station106 also includes transmit/receive (Tx/Rx) circuitry 804 fortransmitting data to and receiving data from UE 102 and transmit/receive(Tx/Rx) circuitry 805 for transmitting data to and receiving data from,for example, a core network node 888. Software 808 is configured suchthat when processor 802 executes software 808, base station 106 performssteps described above (e.g., steps described above with reference to theflow chart shown in FIGS. 4 and 5). For example, software 808 mayinclude: (1) computer instructions (e.g., a RAT layer determiningmodule) for determining the number of layers associated with a RAT toinstruct a UE to monitor, wherein the determined number of layers may be(a) equal to a predetermined maximum number of layers associated withthe RAT or (b) less than said predetermined maximum number of layersassociated with the RAT. The RAT layer determining module may beconfigured to make the determination based, at least in part, oncapability information received from the UE.

Referring now to FIG. 9, FIG. 9 is a functional block diagram of UE 102according to some embodiments of the invention. As shown, UE 102 maycomprise a data processing system 902 (e.g., one or moremicroprocessors), a data storage system 906 (e.g., one or morenon-volatile storage devices) and computer software 908 stored on thestorage system 906. Configuration parameters 910 may also be stored instorage system 906. UE 102 also includes transmit/receive (Tx/Rx)circuitry 904 for transmitting data to and receiving data from abusestation. Software 908 is configured such that when processor 902executes software 908, UE 102 performs steps described above (e.g.,steps described above with reference to the flow chart shown in FIG. 6).For example, software 908 may include: (1) computer instructions (e.g.,a capability information module) for creating a message comprisingcapability information. As discussed herein, the capability informationmay include: (1) radio access technology (RAT) capability informationidentifying a plurality of RATs supported by the UE (each of theplurality of RATs may be associated with a predetermined maximum numberof layers that the UE may be instructed by a network node to monitor)and (2) RAT layer capability information indicating that the UE isconfigured to monitor less than the predetermined maximum number oflayers associated with at least one of the plurality of RATs.

In the foregoing described embodiments, reporting of capabilityinformation can be done in connected mode and may also be reported atthe call setup or in some cases after handover. In one embodiment,capability information is reported via RRC signaling. In idle mode, cellreselection is based on the broadcast parameters. Thus, the network willbroadcast parameters related to all the layers it supports. However, theUE will monitor layers according to its capabilities.

ABBREVIATIONS

-   UE: User Equipment-   UTRAN: UMTS Terrestrial Radio Access Network-   LTE: Long Term Evolution-   CDMA2000 1x RTT: CDMA2000 1x Radio Transmission Technology-   E-UTRAN: Evolution UMTS Terrestrial Radio Access Network-   HRPD: CDMA2000 High Rate Packet Data-   IF: Inter Frequency-   IRAT: Inter RAT-   OFDM: Orthogonal Frequency Division Modulation-   OFDMA: Orthogonal Frequency Division Multiple Access-   WCDMA: Wide Band Code Division Multiple Access-   RAT: Radio Access Technology-   CPICH: Common Pilot Channel-   RSRP: Reference Symbol Received Power-   RSRQ: Reference Symbol Received Quality-   RSSI: Received Signal Strength Indicator-   RAT: Radio Access Technology-   RRC: Radio Resource Control

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not limitation. Thus, the breadth and scope of thepresent invention should not be limited by any of the above-describedexemplary embodiments.

Additionally, while the processes described above and illustrated in thedrawings are shown as a sequence of steps, this was done solely for thesake of illustration. Accordingly, it is contemplated that some stepsmay be added, some steps may be omitted, the order of the steps may bere-arranged, and some steps may be performed in parallel.

What is claimed is:
 1. A method performed by abase station, comprising:receiving capability information from a user equipment (UE), whereinsaid capability information comprises radio access technology (RAT)capability information identifying a set of RATs supported by the UE,wherein each RAT is associated with a predetermined maximum number oflayers that the UE may be instructed to monitor, said predeterminedmaximum number of layers being a standardized value; and for at leastone of said RATs included in the set of RATs: determining the number oflayers associated with the RAT to instruct the UE to monitor, whereinthe determined number of layers is less than said predetermined maximumnumber of layers associated with the RAT, wherein the determination isbased, at least in part, on at least some of the received capabilityinformation; and after the determining step, transmitting to the UE RATlayer monitoring information, wherein the RAT layer monitoringinformation indicates the determined number of layers that the UE shouldmonitor on the RAT.
 2. The method of claim 1, further comprising storingconfiguration information that, for each of a plurality of sets of RATs,associates a number with at least one RAT included in the set, whereinsaid number represents a number of layers associated with the RAT,wherein the determining step comprises accessing said configurationinformation and using said configuration information to determine thenumber of layers associated with the RAT to instruct the UE to monitor.3. The method of claim 2, wherein the step of using said configurationinformation comprises finding the set of RATs included in theconfiguration information that matches the set of RATs identified by theRAT capability information.
 4. The method of claim 1, wherein thecapability information further comprises RAT layer capabilityinformation indicating that the UE is configured to monitor less thanthe predetermined maximum number of layers associated with at least oneof the RATs included in the set of RATs.
 5. The method of claim 4,wherein the RAT layer capability information comprises, for each RATincluded in the set of RATs, a number associated with the RAT, saidnumber representing a maximum layer monitoring capability.
 6. The methodof claim 4, wherein the RAT layer capability information comprises, forat least one of the RATs included in the set of RATs, a numberassociated with the RAT, said number representing a maximum layermonitoring capability and said number being less than the predeterminedmaximum number associated with the RAT.
 7. The method of claim 4,wherein the RAT layer capability information comprises, for each RATincluded in the set of RATs, a single bit, wherein the value of the bitidentifies whether or not the UE is configured to monitor thepredetermined maximum number of layers associated with the RAT.
 8. Abase station, comprising: a receiver operable to receive capabilityinformation transmitted from a user equipment (UE), wherein saidcapability information comprises radio access technology (RAT)capability information identifying a plurality of RATs supported by theUE, wherein each RAT is associated with a predetermined maximum numberof layers that the UE may be instructed to monitor; a RAT layerdetermining module configured to determine the number of layersassociated with a RAT to instruct the UE to monitor, wherein thedetermined number of layers may be (a) equal to said predeterminedmaximum number of layers associated with the RAT or (b) less than saidpredetermined maximum number of layers associated with the RAT, andwherein the RAT layer determining module is configured to make thedetermination based, at least in part, on at least some of the receivedcapability information; and a transmitter operable to transmit to the UERAT layer monitoring information, wherein the RAT layer monitoringinformation indicates the number of layers associated with the RAT thatthe UE should monitor.
 9. The base station of claim 8, furthercomprising a data storage device for storing configuration informationthat, for each of a plurality of sets of RATs, associates a number withat least one RAT included in the set, wherein said number represents anumber of layers associated with the RAT, wherein the RAT layerdetermining module is configured to determine said number of layers byaccessing said configuration information and using said configurationinformation to determine the number of layers associated with the RAT toinstruct the UE to monitor.
 10. The base station of claim 9, wherein RATlayer determining module is configured to use said configurationinformation by finding the set of RATs included in the configurationinformation that matches the plurality of RATs identified by the RATcapability information.
 11. The base station of claim 8, wherein thecapability information further comprises RAT layer capabilityinformation indicating that the UE is configured to monitor less thanthe predetermined maximum number of layers associated with at least oneof the plurality of RATs.
 12. The base station of claim 11, wherein theRAT layer capability information comprises, for each RAT included in theplurality of RATs, a number associated with the RAT, said numberrepresenting a maximum layer monitoring capability.
 13. The base stationof claim 11, wherein the RAT layer capability information comprises, forat least one of the RATs included in the plurality of RATs, a numberassociated with the RAT, said number representing a maximum layermonitoring capability and said number being less than the predeterminedmaximum number associated with the RAT.
 14. The base station of claim11, wherein the RAT layer capability information comprises, for each RATincluded in the plurality of RATs, a single bit, wherein the value ofthe bit identifies whether or not the UE is configured to monitor thepredetermined maximum number of layers associated with the RAT.
 15. Amethod performed by a user equipment (UE) for informing a network nodeof the UE's radio access technology capabilities, comprising:determining that capability information should be sent to the networknode; and transmitting capability information to the network node inresponse to determining that the capability information should be sentto the network node, said transmitted capability information comprisingradio access technology (RAT) capability information identifying aplurality of RATs supported by the UE, wherein each of the plurality ofRATs is associated with a predetermined maximum number of layers thatthe UE may be instructed by the network node to monitor, characterizedin that the capability information further comprises RAT layercapability information indicating that the UE is configured to monitorless than the predetermined maximum number of layers associated with atleast one of the plurality of RATs.
 16. The method of claim 15, whereinthe RAT layer capability information comprises, for each RAT included inthe plurality of RATs, a number associated with the RAT, said numberrepresenting a maximum layer monitoring capability.
 17. The method ofclaim 15, wherein the RAT layer capability information comprises, for atleast one of the RATs included in the plurality of RATs, a numberassociated with the RAT, said number representing a maximum layermonitoring capability and said number being less than the predeterminedmaximum number associated with the RAT.
 18. The method of claim 15,wherein the RAT layer capability information comprises, for each RATincluded in the plurality of RATs, a single bit, wherein the value ofthe bit identifies whether or not the UE is configured to monitor thepredetermined maximum number of layers associated with the RAT.
 19. Themethod of claim 15, further comprising: receiving from the network nodeRAT layer monitoring information, wherein the RAT layer monitoringinformation comprises information indicating the number of layers thatthe UE should monitor on a specified RAT; and in response to receivingthe RAT layer monitoring information, monitoring not more than thenumber of layers on the specified RAT, wherein the number of layers isless than the predetermined maximum number of layers associated with theRAT.
 20. The method of claim 19, wherein the step of monitoring thelayers on the specified RAT comprises identifying new cells belonging tothe layers.
 21. The method of claim 20, wherein the step of monitoringthe layers on the specified RAT further comprises: performing one ormore downlink measurements on the identified new cells; and/orevaluating one or more events associated with one or more of theidentified new cells.
 22. A user equipment (UE), comprising: a receiveroperable to receive information transmitted from a network node; acapability information module configured to create a message comprisingcapability information, said capability information comprising radioaccess technology (RAT) capability information identifying a pluralityof RATs supported by the UE, wherein each of the plurality of RATs isassociated with a predetermined maximum number of layers that the UE maybe instructed by the network node to monitor; and a transmitter operableto transmit the message to the network node, characterized in that thecapability information further comprises RAT layer capabilityinformation indicating that the UE is configured to monitor less thanthe predetermined maximum number of layers associated with at least oneof the plurality of RATs.
 23. The UE of claim 22, wherein the RAT layercapability information comprises, for each RAT included in the pluralityof RATs, a number associated with the RAT, said number representing amaximum layer monitoring capability.
 24. The UE of claim 22, wherein theRAT layer capability information comprises, for at least one of the RATsincluded in the plurality of RATs, a number associated with the RAT,said number representing a maximum layer monitoring capability and saidnumber being less than the predetermined maximum number associated withthe RAT.
 25. The UE of claim 22, wherein the RAT layer capabilityinformation comprises, for each RAT included in the plurality of RATs, asingle bit, wherein the value of the bit identifies whether or not theUE is configured to monitor the predetermined maximum number of layersassociated with the RAT.
 26. The UE of claim 22, wherein the UE isconfigured to monitor layers associated with a RAT by identifying newcells belonging to the layers and performing one or more downlinkmeasurements on the identified new cells and/or evaluating one or moreevents associated with one or more of the identified new cells.
 27. Amulti-modal user equipment (UE) configuration method, comprising:configuring the UE so that it supports a plurality of radio accesstechnologies (RATs), wherein each of the plurality of RATs is associatedwith a predetermined maximum number of layers that the UE may beinstructed by a network node to monitor simultaneously; configuring theUE so that it is operable to transmit to the network node capabilityinformation, said capability information comprising RAT capabilityinformation identifying the plurality of RATs supported by the UE; andconfiguring the UE to monitor simultaneously not more than X layersassociated with one of the plurality of RATs, wherein X is less than thepredetermined maximum number of layers associated with the RAT.
 28. Themethod of claim 27, wherein the capability information further comprisesRAT layer capability information indicating that the UE is configured tomonitor less than the predetermined maximum number of layers associatedwith at least one of the plurality of RATs.
 29. The method of claim 28,wherein the RAT layer capability information comprises, for each RATincluded in the plurality of RATs, a number associated with the RAT,said number representing a maximum layer monitoring capability.
 30. Themethod of claim 28, wherein the RAT layer capability informationcomprises, for each RAT included in the plurality of RATs, a single bit,wherein the value of the bit identifies whether or not the UE isconfigured to monitor the predetermined maximum number of layersassociated with the RAT.
 31. The method of claim 27, wherein the UE isconfigured to monitor layers associated with a RAT by identifying newcells belonging to the layers and performing one or more downlinkmeasurements on the identified new cells and/or evaluating one or moreevents associated with one or more of the identified new cells.